For business continuity and user satisfaction, a computer system/service is required to be available for its users at all times. However, computer systems do fail and the computer system/service still needs to be available. One solution is to have a second computer shadow the first computer system by continuously updating its state to match the state of the first computer system. If the first computer system fails (e.g., crashes) and this is detected, then the user can be switched to the second system and operate as if still connected to the first computer. A problem with this solution is that as the number of users and sessions grows, more and more communication is required in order for the second computer to match its state to that of the first computer. It would be beneficial for a system to be able to match states between a first system and a second system especially as the number of users and sessions increase.